Rotten Log Lab - Logistics

Time
45-55 minutes

Grouping
Groups of 4-6 students per log

Materials
For each student:

• Copy of the Rotten Log Questions

For each group of students:

• 1 rotting log, preferably with lots of mushrooms, moss, fungi, termites, beetles and other creepy crawlies in and around the log
• 1 large plastic wash basin or large heavy duty yard waste trash bag to keep the log in
• Work gloves
• Screwdriver, shovel, pry bar, hammer or other tools that can be used to pry open sections of the log
• Bug boxes
• Newspaper to cover the tables

Optional: To see the protozoa in the termites’ gut

• Termite
• Microscope
• Glass slides
• Cover slips
• 2 pairs tweezers
• toothpick
• 0.6% NaCl (0.6 g NaCl in 100 ml water)
• eyedropper

Setting
Classroom

Rotten Log Lab - Background

Teacher Background
I used this activity as a lab-based test that the kids didn’t actually think was a test. It was a super way for them to reveal the holes in their understanding before the written test. Some of the major concepts that can be assessed in this lab include differentiating between a community and an ecosystem, creating food webs, identifying interactions between organisms and between organisms and their environment, predicting the effects of human impact on populations, and assessing ecosystem sustainability.

In addition, I was able to show them an amazing symbiotic relationship between termites and protozoa. Termites eat wood but cannot completely digest the wood on their own. Many varieties of protozoa, single celled animals with amazingly varied modes of locomotion, live in the termites hindgut and help digest the cellulose in the wood. They attach themselves to the inner wall of the termite’s gut to keep from being excreted with undigested wood particles. In return for their invaluable services, the protozoa get a nice, safe home and a constant supply of food.

Student Prerequisites
Knowledge of food webs, ecosystems, organism-environment interdependence, and sustainability.

Rotten Log Lab - Getting Ready

Getting Ready

1. Find some nice, juicy, moss and mushroom covered, termite and beetle infested logs. You know you’ve found a good log if you can pull off chunks of wood with your hands. I discovered mine (8 logs, enough for my students in groups of 4) in a wooded area of Golden Gate Park. You can use the same log with 2 successive groups of students if you just make sure the first group doesn’t go crazy with the hammer. You can also flip the log over for the second group. I found that the best time to go log hunting is after a month of nice, wet weather after mushrooms have begun to appear.
2. Make copies of the Rotten Log Questions
3. Cover your tables with newspaper
4. Set out logs and the group materials

Optional: Set up protozoa viewing station. I would practice extracting protozoa on your own first. The protozoa are active for around 2 hours before they stop moving so you’ll need to set up a new slide every few hours.

1. To extract the protozoa, first find a termite and put it on a glass slide. Use one pair of tweezers to hold its head and the other to hold its rear. Slowly and firmly pull apart. You should see a long, stringy tube, the hindgut. If you don’t squeeze the rear end with the tweezers until you do.
2. Place a drop of saline on the hindgut and mash the hindgut with the tweezers or a toothpick. If the hindgut never came out at all, you can mash the entire rear end.
3. Cover with a coverslip.
4. Observe under the microscope. Look for a mass of writhing stuff. You should be able to zoom in and observe individual protozoa and see differences between the many species that are present.

Rotten Log Lab - Lesson Plan

Lesson Plan

1. It’s pretty useless trying to hold the kids attention when there are moss and mushroom covered logs on the tables. Thus, give the students the question sheet right away and let them go once you read the rules:
2. Use any of the tools provided.
3. Don’t harm any organisms.
4. You may carefully break small pieces of the log apart but NO SMASHING. Keep all the pieces of the log in the basin, NOT all over the table or the floor.
5. Have students answer the questions in a lab notebook or on a separate sheet of paper. The questions are on the student Rotten Log Questions download but are also listed again here for your convenience:

• List as many organisms in the ecosystem as you can find. For each organism, draw a picture and label it with a name that describes the organism like “light-brown, long bodied ant-like thing” or “2 cm-long black beetle”. More things are living than you might think…
• List as many non-living parts of the environment as you can find. There is more than just wood – think about solids, liquids AND gases!
• Which of the things you just listed are part of the log community?
• Which of the things you just listed are part of the log ecosystem?
• What is the difference between a community and an ecosystem?
• Find evidence about the food webs that make up the community. Do you see any organisms eating? Do you see any “poop” that gives a hint about what the organisms have been eating? Draw as much of the food web as you can.
• Describe one organism-organism interaction that you observe.
• Describe one organism-environment interaction that you observe.
• How will this lab impact the populations of organisms in your log? Pick one organism and describe how the population of this species will be affected by our investigation.
• Is this ecosystem sustainable? Why or why not? Use your observations to support your idea.
• If you have a protozoa viewing station set up, invite groups one at a time to come visit you at the microscope to see the protozoa.
• Reserve plenty of time to clean up.

Rotten Log Lab - Going Further

Going Further
Another cool termite trick… Did you know that termites mistake the smell of a Bic pen for a pheromone that they use to navigate? Pheromones are chemicals that communicates a message to other members of the same species. Although humans do have pheromones, termites and other social insects communicate extensively through these chemical messages. Termite workers indicate the path to a food source by leaving behind a trail-pheromone. A chemical in Bic pens (not other pens for some reason) mimics the trail-pheromone. If you draw a line with a Bic pen on paper then place a termite on the line, the termite will faithfully follow the line wherever it leads. Try drawing curly-Qs and other shapes. See what happens when a termite hits a crossroads. Try pens by other manufacturers. Try different colors of Bic pen.

Rotten Log Lab - Sources and Standards

Sources
The idea for this activity came from a workshop by Karen Kalamuck at the Exploratorium. THANK YOU Karen!

If you just can’t be bothered to go find rotting logs but really want to try the termite activities, termites can be ordered from Carolina Biological with instructions for how to isolate the protozoa ($11.25) OR with instructions for how to draw lines with Bic pens ($32.75).

Standards
Grade 6
Ecology (Life Sciences)
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment.

All Grades
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations.